Murderous loki

So rather than bash on you unprovoked like the discourteous Dr. Floki I thought I'd provide some constructive criticism. A few tips here and there to explain the general go-to Loki build and his use.

So firstly, what is Loki really good at? He has very high burst damage on a single target, he's very hard to kill due to his Vanish and Assassinate and he has very good lane clear with his decoy. Due to these traits, people generally build and play Loki to do two tasks:
1) to take out towers/phoenixes (ie: split push) with his high dps, good lane clear, and his ability to absorb tower damage with decoy and run away when chased with Vanish
2) assassinate squishy targets before running away (eg: the enemy mid laner or ADC).

Before anything else, we must determine where Loki is best suited? While Loki can be a decent jungler, he lacks the ability to push towers there, get a lot of farm while safely clearing, or be a real contribution to early-mid game team fights. Thus most players choose to place him in the solo lane where he can simply clear waves during his mediocre early game phase and then push towers quickly and force the enemy solo laner to either stay in lane with him or lose two towers before they can blink. To do this players will usually grab teleport as their first relic so that once they're low on mana/health they can quickly go back to base, or go gank a lane quickly when given an opportunity. To clear waves, players will level up decoy first, from there the priority shifts to Assassinate, aimed strike and finally Vanish.

Finally, we must determine what build is best suited for Loki. We want to prioritize ability damage (and movement to both get around the map, pursue and escape), thus the best way to do this is through power, penetration and cooldown reduction. Most players will grab Transcendence first both for the extra mana and power, thus helping them clear lane. Then move onto Warrior Tabi for the power and much needed movement speed, Jotunn's Wrath (benefits all your key qualities for a low price), and from there grab power/penetration items like Titan's Bane, The Crusher (also great for tower pushing), and Brawler's Beat Stick. If you're comfortable with auto-attack cancelling (cancelling an ability into an auto-attack to reset your attack chain), Hydra's Lament is also a great option.

Crits while powerful, don't affect towers at all making them ineffective for split pushing, and leave your dps very unreliable (while you may kill someone once because you have 20% crit chance, you're only doing so 1/5 times). Hastened Fatalis is good for auto-attackers that need a few hits to secure a kill, but Loki only needs to land 1-3 hits to secure a kill on any squishy target, and 2 are guaranteed with the third being fairly easy to follow up with with experience (or an ulti).

Just to show why people prefer the build suggested above, lets take your build and compare their damage and cost against an Artemis (assuming that as an ADC she's not building protections). The usual build ( Transcendence -> Warrior Tabi -> Jotunn's Wrath -> The Crusher -> Titan's Bane -> Brawler's Beat Stick) costs 13440g and will deal 1904 damage with Vanish, aimed strike and two auto-attacks (one of which activates them), and will deal 3074 with an added Assassinate and its guaranteed auto-attack. Both of these are more than Artemis 1890 health pool, meaning you can 100-death her without an ulti, in two auto-attacks, WITHOUT backstabbing her.

Now let's compare that. Your build costs 16030g (a full 2500g more expensive, ie: a full item). Your average damage with a Vanish, aimed strike and two autos is 1449. Assuming both autos are crits (1/25 chance) your damage is still only 1899. Finally, with that and an extra auto + Assassinate, your average damage is 2310. Assuming 3 crits (1/125 chance), your damage is still less than the recommended build capping at 2985.

Thus, this is likely why you found a need for Hastened Fatalis, you're not killing targets as quickly as you should, so you're relying on an extra 2-3 unnecessary auto-attacks using Hastened Fatalis' sticking power, Qin's Sais passive boost and crit unreliability to finish off squishy targets.

Hopefully this has been informative and constructive criticism. I hope you continue to enjoy Loki and become ever better!

~Zilby